Respiratory treatment apparatus commonly include means to alter the humidity of a provided breathable gas in order to reduce drying of the patient's airway and consequent patient discomfort and associated complications. The use of a humidifier placed between the flow generator of such an apparatus and the patient interface, produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. The humidifier is generally placed between the flow generator and the air delivery conduit, with the air delivery conduit being attached to the patient interface unit.
As schematically shown in FIG. 1, a respiratory treatment apparatus, for example a Continuous Positive Airway Pressure (CPAP) system, generally includes a positive airway pressure (PAP) device 2000 with a flow generator, a humidifier 2005, an air delivery conduit 2010 (also referred to as a tube or tubing), and a patient interface 2030. The air delivery conduit 2010 is coupled to the outlet 2012 of the humidifier 2005. In use, the respiratory device 2000 generates a supply of pressurized air that is humidified by the humidifier 2005 and delivered to the patient via an air delivery conduit 2010 that includes one end coupled to the outlet 2012 of the humidifier 2005 and an opposite end coupled to the inlet 2014 of the patient interface 2030. The patient interface comfortably engages the patient's face and provides communication with the patient's airways. The patient interface or mask may have any suitable configuration as is known in the art, e.g., full-face mask, nasal mask, oro-nasal mask, mouth mask, nasal prongs, etc. Also, headgear may be utilized to comfortably support the patient interface in a desired position on the patient's face.
Many humidifier types have been proposed, including humidifiers that are either integrated with or configured to be coupled to the relevant respiratory treatment apparatus. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that patient will be comfortable.
Humidifiers may typically include a water tub having a capacity of several hundred milliliters, a heating element for heating the water in the tub, a control to enable the level of humidification to be varied, a gas inlet to receive gas from the flow generator, and a gas outlet adapted to be connected to a gas conduit that delivers the humidified pressurized gas to the patient's interface unit.
Air delivery conduits are generally used to connect a patient interface to a respiratory humidifier system to enable delivery of the humidified gas flow to the patient. Air delivery conduits are available in a variety of lengths and diameters. For respiratory conduits, a standard tubing may have an external diameter of 22 mm (internal diameter 19 mm) and lengths of 1.8 meters or 2 meters. Smaller conduits or tubing diameters such as 15 mm tubing may be used as described in co-pending U.S. application Ser. No. 12/461,967 filed 28 Aug. 2009, the content of which is incorporated herein in its entirety.
Both unheated and heated air delivery conduits are known to be used with CPAP and ventilation systems. The conduits are generally attached to the outlet of the humidification system at one end and to a patient interface unit at the opposing end. In such humidification systems a common problem can occur with rainout within the air delivery conduit. The humidified air may cool on its path along the conduit from the humidifier to the patient, leading to the phenomenon of “rain-out”, or condensation, forming on the inside of the conduit. In use, heated air delivery conduits assist in addressing the issues with rainout or condensation within the conduit. For example, a heated conduit may maintain a desired temperature throughout the heated conduit preventing the cooling of the humidified gas flowing through it during operation of the respiratory treatment apparatus.
However, rainout or condensation may also occur when the system is turned off after use when the humidified air remaining within the system begins to cool. Some systems include or recommend a controlled cool down period for the humidifier and/or the heated conduit to assist in reducing the level of rainout. However, some rainout or condensation still tends to occur within the conduit. The presence of condensation or moisture within the conduits can lead to bacterial or microbial growth within the conduits and hygiene issues.
It may be desirable to develop devices to reduce rainout or condensation within conduits attached to humidification systems such as when humidification is no longer being provided or when the system is turned off.